Energy storage and conversion devices

Abstract

An energy conversion and storage device (1) which comprises a magnetic rotor (5) and a stator (7) comprising one or more electric coils whereby electrical energy may be applied to and extracted from the device (1) when the rotor (5) is rotating relative to the stator (7) and means (13, 14, 15, 17) for electromagnetically suspending the rotor (5) whilst rotating relative to the stator (7), wherein the rotor (5) comprises a tubular body portion formed of a composite of fiber reinforced material and magnetic material emnbedded within the fiber reinforced material and the stator (7) is disposed inside the rotor (5) co-axially with the rotor (5) and extends along at least a major part of the length of the said body portion of the rotor (5).

We claim: 
     
       1. An energy conversion and storage device which comprises a magnetic rotor and a stator comprising one or more electric coils whereby electrical energy may be applied to and extracted from the device when the rotor is rotating relative to the stator and means for electromagnetically suspending the rotor whilst rotating relative to the stator, wherein the rotor comprises a body portion formed of a composite of fiber reinforced material and the stator is disposed inside the rotor co-axially with the rotor; wherein the body portion of the rotor is a hollow tubular cylinder and has a length along its axis which is greater than its widest diameter; magnetic material is embedded within the fiber reinforced material of the body portion of the rotor; and the stator extends along at least a major part of the length of the said body portion of the rotor. 
     
     
       2. A device as in claim 1 and wherein the length of the body portion faces the stator over at least 90 per cent of the length of the stator. 
     
     
       3. A device as in claim 1 and wherein the stator is formed using a substrate comprising a die cast or sintered or extruded or moulded tube or cylinder, the substrate ccmpri-sing ironless metallic or polymeric material. 
     
     
       4. A device as in claim 1, and wherein the stator has means associated therewith by which iroi particles suspended in a pumpable fluid may be injected into or removed from a cavity within the stator whereby the permeability of the stator may be varied according to the reauired state of energisation of the device. 
     
     
       5. A device as in claim 1 and wherein the rotor and stator are contained in an enclosure defining a chamber which may be evacuated to a high vacuum state during use to minimise molecular drag upon the rotor and the parasitic energy losses produced thereby. 
     
     
       6. A device as in claim 5 and wherein the chamber includes an arrangement by which residual molecules may be accelerated toward and through a semi-permeable membrane and trapped in a region of the chamber behind the membrane to assist,develop and maintain the vacuum. 
     
     
       7. A device as in claim 6 and wherein the membrane comprises a microporous material which allows gas molecules through at high speed but does not allow back transmission at low speeds. 
     
     
       8. A device as in claim 6 and wherein the semi-permeable membrane is provided in the space between the rotor and the enclosure inner wall whereby the membrane may be penetrated in use by residual gas molecules projected toward the membrane by the rotary action of the rotor and thereafter trapped in the region between the membrane and the enclosure inner wall. 
     
     
       9. A device as in claim 8 and wherein the membrane is corrugated to increase the probability of molecules being projected through the membrane. 
     
     
       10. A device as in claim 5 and wherein the device includes a hollow conduit through which coolant fluid may be passed to remove heat generated during use. 
     
     
       11. A device as in claim 10 and wherein the conduit comprises a hollow shaft located substantially on the axis of the stator and extending between the respective facing end walls of the enclosure. 
     
     
       12. A device as in claim 5 and wherein the inner wall of the enclosure comprises means to arrest the material of the rotor in the event that the rotor crashes into the enclosure following malfunction during use. 
     
     
       13. A device as in claim 1 and wherein in order to detect an impending failure of the rotor in the device, the device includes means for monitoring the temperature in the said chamber or of the rotor and/or for monitoring the stress patterns developed in the body of the rotor. 
     
     
       14. A device as in claim 13 and wherein fiber-optic guides are used to monitor remotely temperatures or stress patterns of the rotor. 
     
     
       15. A device as in claim 1 and wherein the coil or coils of the stator are connected to an external switching circuit which allows the device to function alternatively as an electric generator or an electric motor, the switching circuit allowing input electrical energy to be applied to the coils to be stored as kinetic energy by the rotor. 
     
     
       16. A device as in claim 1 and wherein the said tubular body portion of the rotor comprises a tube whose cross-sectional area varies along its length or part of its length. 
     
     
       17. A device as in claim 1 and wherein the gap between the rotor and stator is substantially constant along the length of the said body portion of the rotor. 
     
     
       18. A device as in claim 1 and wherein the arrangement of the rotor and stator is such that the magnetic fields generated in use between the two extend substantially orthogonally to the axis of the rotor.